Pen



FIG. 1 is a top plan view of a pen in accordance with my new design;

FIG. 2 is a bottom plan thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a left side elevational view thereof; and,

FIG. 6 is a right side elevational view thereof. 

The ornamental design for a pen, as shown and described. 